In co-pending application Ser. No. 08/063,241 and in U.S. Pat. No. 5,096,033, issued on Mar. 17, 1992, the problems that have been encountered in the unattended acceleration of a vehicle in shifting from the park position to the other gear positions were explained. Such problems prompted efforts which have been made to prevent the shifting of the shift lever until the brake pedal had been depressed so that the vehicle does not move before it is intended by the driver. U.S. Pat. No. 5,096,033 discloses an electrically operated control module mounted on a detent plate and having a pin movable between a distended position to an extended position. This control module is controlled by the application or nonapplication of the brakes of the vehicle in which the shifter is mounted. When the brakes are not applied, the pins are to an extended position which prevents a lockout arm from being moved by the actuation of the pawl actuator and, accordingly, the pin, when extended, prevents the shifting of the shift lever. However, when the pin is distended by applying the brakes, it is located out of the path of the lockout arm, permitting the actuation of the pawl and the shifting of the shift lever from park position to other gear positions.
In the co-pending application Ser. No. 08/063,241, it was pointed out that there are other types of lockout mechanisms that have been devised. One such suggested mechanism was to mount an electrically operated control module having a pin movable between a distended position to an extended position on the tube of a shift lever. In such mechanism, the pin was movable in response to the energization of the coil of the module to an extended position and into the path of pawl actuator. The pin actually was an armature forced by the magnetic field of the coil into a notch formed in the side of the pawl actuator locking the pawl actuator against movement by the driver. Both the pin and the notch included angled sides which engaged each other so that when the coil was not energized, the pin was cammed out of the way of the pawl actuator permitting the driver to move the pawl out of the park/lock position. In this proposed design, the axial center of the coil of the module in the pin extended along an axis parallel to the pawl actuator and the pin was held in the notch of the pawl actuator by a magnetic force and was withdrawn from the notch by a spring. This arrangement resulted in a temporary binding force between the pawl actuator and the pin which gave an undesirable feel to the driver. As a result, it was contemplated to provide two similar modules spaced one above the other in an attempt to eliminate such binding. Such previous design also had the decided disadvantage of cost in requiring constant energization of the coils during the park/lock condition of the shifter.
Co-pending patent application Ser. No. 08/063,241, of which this application is a continuation-in-part, discloses a simplified, lower cost version of a brake/park lock mechanism for preventing a driver from shifting a shift lever from park position to another gear position unless the brake is applied. Such device includes the combination of a locking member and mechanical advantage means for actuating the locking member by applying a force on the mechanical advantage means in a direction substantially orthogonal to the direction of the movement of the locking member. Such combination takes advantage of the lesser force required to move the locking member into locked position, and the greater force exerted by the mechanical advantage means in holding the locking member in locked position.
More specifically, the device of application Ser. No. 08/063,241 discloses a unique mechanical advantage means which comprises a toggle joint operatively connected between the actuator of the electrical module and the locking member, thus utilizing the mechanical advantage of the toggle joint. Therefore, in the locked position of the locking member, the toggle joint is capable of withstanding the inadvertent force a driver might exert on the pawl actuator without applying the vehicle's brakes. The toggle mechanism includes at least two links which are pivotally connected together at one of their ends at a point referred to hereinafter as the "knee." At their other ends, one of the links is pivoted about a fixed axis and the other end of the link is slidable and connected to the locking member. When the two links are aligned or nearly aligned with the pivotal axis of the knee on the center line between the pivotal axes of the other ends of the links, the force required on the locking member substantially along such center line to pivot the two links is tremendous. However, if the pivotal axis or knee of the two links is moved a sufficient distance off center in one direction, the two links can be pivoted relative to each other with very little force on the locking member. Thus, as the distance between the center line and the axis of the knee between the two links increases, the amount of force required to move the pawl actuator decreases.
The device of application Ser. No. 08/063,241 takes advantage of the above phenomenon by applying a force to the knee between the links toward the center line by a biasing means such as a spring, until the knee reaches the center line or slightly beyond where it abuts against a stop. At such position, the locking member is immovable until the module actuator, which is movable in response to the coil of the module and is connected to the toggle joint at the pivotal axis or knee between the two links, pulls the knee away from the center line, thus greatly reducing the restraining force of the toggle.
The present invention also takes advantage of the above phenomenon by applying a force to the knee between the links in a direction toward the center line by a permanent magnetic force until the axis of the knee reaches a position slightly above the center line. At such position, the locking member is immovable until a repelling magnetic force is exerted on the knee to force the knee away from the center line, thus greatly reducing the restraining force of the toggle and, in fact, moving the locking member to an unlocked position.
The magnetic attracting and repelling forces exerted on the knee between the links toward and away from the center line are created by a permanent magnet associated with the module actuator. The polarized permanent magnet is attracted to a metal core surrounded by a coil that is energized in response to the application of the brakes of the vehicle. Thus, in the locked position of the knee of the toggle joint, the permanent magnet is attracted to the metal core to move and hold the locking member in locked position. However, when the coil is energized, it changes the magnetic pole at the end of the metal core, causing the polarized permanent magnet to be repelled and thus, the central axis of the knee to be forced away from the center line so as to reduce the restraining force of the toggle and, in effect, withdraw the locking member out of the locked position.
Having briefly described the physical features of the invention, the following drawings with the more detailed description will serve to explain the concepts and principles of the invention.